Re: [PATCH net 1/1] net: tcp: Permit user set TCP_MAXSEG to default value

[Eric Dumazet]

On Tue, 2017-03-21 at 05:30 +0800, f...@ikuai8.com wrote:
> From: Gao Feng 
> 
> When user_mss is zero, it means use the default value. But the current
> codes don't permit user set TCP_MAXSEG to the default value.
> It would return the -EINVAL when val is zero.
> 
> Signed-off-by: Gao Feng 
> ---
>  net/ipv4/tcp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1e319a5..dd5e8e2 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2470,7 +2470,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
>   /* Values greater than interface MTU won't take effect. However
>* at the point when this call is done we typically don't yet
>* know which interface is going to be used */
> - if (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
> + if (val < 0 || (val > 0 && val < TCP_MIN_MSS) ||
> + val > MAX_TCP_WINDOW) {
>   err = -EINVAL;
>   break;
>   }

This is a convoluted way to express that val == 0 is accepted ...

What about :

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 
1e319a525d51b0b603a5ccc5143381c752b9f2c7..7db78d72896ac7c4befba5966704ed18ecbac409
 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2469,8 +2469,9 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
case TCP_MAXSEG:
/* Values greater than interface MTU won't take effect. However
 * at the point when this call is done we typically don't yet
-* know which interface is going to be used */
-   if (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
+* know which interface is going to be used.
+*/
+   if (val && (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW)) {
err = -EINVAL;
break;
}

[PATCH net 1/1] net: tcp: Permit user set TCP_MAXSEG to default value

[fgao]

From: Gao Feng 

When user_mss is zero, it means use the default value. But the current
codes don't permit user set TCP_MAXSEG to the default value.
It would return the -EINVAL when val is zero.

Signed-off-by: Gao Feng 
---
 net/ipv4/tcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1e319a5..dd5e8e2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2470,7 +2470,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
/* Values greater than interface MTU won't take effect. However
 * at the point when this call is done we typically don't yet
 * know which interface is going to be used */
-   if (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
+   if (val < 0 || (val > 0 && val < TCP_MIN_MSS) ||
+   val > MAX_TCP_WINDOW) {
err = -EINVAL;
break;
}
-- 
1.9.1